“You know how impassioned these stakeholders are,” Rep. Lois Capps, the Democratic congresswoman from Santa Barbara whose district includes Diablo Canyon, said in an interview Tuesday.

But even as Diablo Canyon joins other nuclear plants on the pending-shutdown roster, new facilities will be coming online elsewhere, and Diablo Canyon’s fate does not necessarily foreshadow more closures to come.

“This agreement is unique to PG&E and California energy policy,” stated Marvin Fertel, president and chief executive officer at the Nuclear Energy Institute, which advocates for nuclear energy in Washington.

San Luis Obispo, California, resident Gene Nelson, government liaison for Californians for Green Nuclear, added in an e-mail exchange that “this decision indicates the severe shortcomings in the California and the national regulatory environment.”

Currently, 99 nuclear reactors operate in the United States. Together, they account for 19.5 percent of U.S. electricity production.

In 1985, when the first of Diablo Canyon’s two reactors powered up, nuclear plants generated 15.5 percent of the nation’s electricity. For all its continuing controversy, nuclear’s share of overall U.S. electricity production has remained relatively constant for the past 25 years.

Four nuclear power plants shut down in recent years. Between 2017 and 2019, an additional five facilities will be shuttered prior to the expiration of their licenses.

The Nuclear Energy Institute attributes six of these power-plant closures to “market” conditions, meaning utilities determined these plants no longer made economic sense. Two closures were attributed to “mechanical” problems, like those that forced permanent shut-down in 2013 of the San Onofre plant near San Diego.

The planned 2019 closure of the nation’s oldest operating facility, the Oyster Creek power plant in New Jersey, was attributed to a “policy” that resulted from negotiations with the administration of Gov. Chris Christie.

Four new reactors are under construction, in Georgia and South Carolina.

Under the new Diablo Canyon agreement made public Monday, PG&E agreed with a number of local environmental groups to let the licenses for the facility’s two reactors expire in 2024 and 2025. The utility will boost its investments in renewables, energy efficiency and storage. In return, the local groups will back PG&E’s application to renew its license to operate the plant’s used fuel storage plant.

“Hopefully, this timeline will give time to see the transition to clean, renewable energy,” Capps said, adding that “we want to make sure the area is satisfied as this major transition proceeds.”

The challenging terrain for those that remain includes political as well as operational hazards, epitomized by the dispute over the proposed waste storage site at Yucca Mountain in Nevada. The facility was designed to hold 70,000 metric tons of high-level waste, primarily spent fuel.

The Bush administration and Congress approved the Yucca Mountain site in 2002, but work was subsequently stopped under the Obama administration.

“Several (Energy Department) officials told us that they had never seen such a large program with so much pressure to close down so quickly,” the non-partisan Government Accountability Office noted in a 2011 report.

Without a permanent storage facility, the nation’s stock of nuclear waste that grows by about 2,000 metric tons each year is spread out among some 75 sites in 33 states.

Businessman Donald Trump, the presumptive Republican presidential nominee, has voiced strong support for nuclear power, telling a Fox News interviewer in 2011, “We do need nuclear energy.” His Democratic rival, Hillary Clinton, has opposed Yucca Mountain but wavered on the overall question of nuclear energy; currently, she supports investing in the nuclear sector with grants.

Congress, too, can direct nuclear’s future. The steadfast opposition of top Senate Democrat Harry Reid of Nevada, formerly the Senate majority leader, was, for instance, instrumental in shutting down Yucca Mountain, and nuclear industry skeptics abound on the left side of Capitol Hill.

“The news that nuclear power will be replaced by renewables is heartening.” Democratic Sen. Barbara Boxer said upon hearing about Diablo Canyon’s upcoming closure.

At the same time, the House last February passed on voice vote a bill by Texas Republican Randy Weber designed to speed work on “advanced nuclear energy technologies.” The measure united, for a moment, lawmakers in their assessment of the nuclear industry’s challenges.

“There have been construction difficulties, regulatory hurdles, and financing issues, all of which have conspired to delay the construction of new nuclear plants in America,” Rep. Don Beyer, D-Virginia, said during House debate.